Numerical Simulation of Heat Transfer and a Forging Plate Structure in a Radiant Syngas Cooler with Radiation Screens

Abstract

High-temperature syngas is produced by entrained-flow coal gasification. A traditional quenching process has the drawback of low heat recovery efficiency, and the cleaning of convective syngas cooler is a big problem. Thus, the combination of a radiant syngas cooler and a quench chamber is a more promising way for heat recovery and syngas preliminary purification. In this study, based on the traditional radiant syngas cooler, sixteen radiation screens are added to increase the heat exchange area, so as to further improve heat recovery efficiency of the radiant syngas cooler. Heat transfer and structure analysis of a forging plate on the top of the radiation screen are carried out by numerical simulation. The radiation screen changes the internal spatial structure of the radiant syngas cooler, which also affects the heat transfer characteristics of the membrane wall. The circumferential temperature distribution of the cylinder membrane wall is not uniform, and the temperature is the highest at the central pipe. The surface heat flux of the cooling pipes on the radiation screen reaches the maximum value at the position with a distance of about 6 m from the top. The slag and fly ash carried in the gas flow deposit on the wall surface and form deposition layers, which protects the forging plate and cooling pipes, but reduces the heat transfer efficiency.

Performance evolution of industrial radiant syngas cooler with radiation screens using numerical simulation

“…The maximum temperature is 684 K, which is within the safe working temperature range of the material (823 K for 15CrMo steel). [ 23 ] With the formation of deposition layers, the surface temperature of the circumferential membrane wall increases gradually, and the high‐temperature zone is formed in the mid‐upper section. The radiation screen is located in the channel of the RSC, and the ash and slag layers are more likely formed on the surface of the radiation screen than on the circumferential membrane wall.…”

“…Radiant cooling is a method of introducing the raw syngas into a radiant syngas cooler (RSC), which is a counter flow heat exchanger. [ 23 ] The syngas moves downward along the central flow channel, and the cooling water of the boiler flows from bottom to top in the circumferentially arranged cooling pipes. [ 24 ] The main function of the RSC is to generate steam through heat recovery.…”

“…However, due to the serious problem of slag blocking, the development and application of this equipment has gradually tapered off. [28] By contrast, the combined radiation-quenching method is more friendly for syngas cooling, which is a system connecting an RSC and a quench chamber, [16,23,29] as shown in Figure 1. The high-temperature syngas produced by the gasification reactions passes through the RSC and quench chamber in turn.…”

Numerical Simulation of the Integral Thermal Deformation Behavior of a Radiant Syngas Cooler for an Entrained-Flow Gasifier

“…Due to the existence of high temperature, high dust, and strong reducing atmosphere in the RSC, it is difficult to directly verify the thermal deformation, but the thermal deformation is mainly affected by the temperature factor of the membrane wall. Hence, the accuracy of the model is indirectly verified by comparing the membrane wall surface temperature with that reported in the literature . The relative error between the simulation and the literature results is represented by η . η = | T ref − T sim T ref | × 100 % where T ref is the literature result and T sim is the simulation result.…”

Numerical Simulations of Solidification Characteristics of Molten Slag Droplets in Radiant Syngas Coolers for Entrained-Flow Coal Gasification

“…A radiant syngas cooler (RSC) is regarded as a crucial heat-recovery device in entrained-flow coal gasification units. − The syngas produced from the gasifier enters the RSC, carrying a great number of fly ash particles and molten slag droplets, and all of them transfer heat to the membrane wall. , However, the molten slag droplets may collide with the membrane wall and the bottom cone of the RSC, and they are more likely to deposit on the wall when they are in the molten state. , The slag deposition and accumulation will strongly affect the heat-recovery efficiency and the safety operation of the RSC. , Hence, it is of great importance to gain a clear understanding of the heat transfer and solidification characteristics of molten slag droplets in the industrial RSC.…”